1. Field of the Invention
The present invention relates to a projector-type vehicle headlamp. More specifically, the present invention relates to a vehicle headlamp operable to irradiate an overhead sign.
2. Background Art
A projector-type vehicle headlamp is configured such that light emitted from a light source disposed on an optical axis extending in a longitudinal direction (a front-and-rear direction) of the vehicle close to the optical axis is reflected in a forward direction by a reflector. The reflected light is irradiated in a forward direction of a lamp through a projection lens provided in front of the reflector.
In a case in which such a projector-type vehicle headlamp is adapted for a low beam (dipped beam) irradiation, a shade, which shields a part of the light reflected by the reflector and removes an upward irradiation light, is provided between the projection lens and the reflector. Thus, a beam is irradiated in a forward direction in a low beam light distribution pattern having a predetermined cutoff line.
In the projector-type vehicle headlamp, the upward irradiation light is removed almost completely by the shade. For this reason, an overhead sign (hereinafter referred to as OHS) disposed above a road surface in the forward direction of the vehicle cannot be seen clearly.
Therefore, there has been proposed a vehicle headlamp in which an auxiliary reflector for causing a part of a light reflected by a reflector to be incident as an upward irradiation light on the projection lens is provided extending toward the projection lens side from the vicinity of an upper edge of the shade and an OHS irradiation light for irradiating the OHS is obtained by the upward irradiation light incident on the projection lens by the auxiliary reflector (for example, see JP-A-7-29402).
However, in a case in which the auxiliary reflector for causing a part of the light reflected by the reflector to be incident as the upward irradiation light on the projection lens is provided in the vicinity of the upper edge of the shade for forming a cutoff line as in the vehicle headlamp which has been described in JP-A-7-29402, a main light distribution reflected by the reflector and passing through the vicinity of the upper edge of the shade is intercepted by the auxiliary reflector. For this reason, there is a possibility that an insufficient quantity of light of the main light distribution might be caused.
In the above vehicle headlamp, a light distribution pattern is formed by the OHS irradiation light so as to be continuous just above the cutoff line of a low beam light distribution pattern formed by the shade. Consequently, there is a possibility that the OHS irradiation light might cause glare for a car running on an opposing lane if a quantity of the light reflected by the auxiliary reflector is large.
Therefore, there has been proposed a technique for regulating deposition treatment (i.e., regulating a thickness of a reflecting film) in order to reduce a quantity of the light reflected by an auxiliary reflector formed with a reflecting surface by depositing a reflecting film on a surface of a transparent member. However, a great deal of time and labor is required for the process of forming the reflecting film through deposition, thereby causing an increase in cost.